Electric vehicles (EV), hybrid-electric vehicles (HEVs), and other vehicles may include a high-voltage power net and a low-voltage power net. The low-voltage power net may be grounded to the vehicle chassis whereas high-voltage power net may be configured with a floating ground, i.e., not grounded to the vehicle chassis. Because the high-voltage power net is not grounded to the same ground as the vehicle chassis, a potential exists for electrical discharge between the high-voltage power net and the low-voltage power net. In some cases where the high-voltage power net is sufficiently great, it may be desirable to provide a certain amount of insulation between the high-voltage power net and the low-voltage power net, which may be quantified as insulation resistance.
The desired amount of insulation resistance may vary depending on the magnitude of the voltage being carried over the high-voltage power net and/or a voltage differential between the high-voltage power net in the low-voltage power net. The amount of insulation resistance may be related to an amount of impedance between the high-voltage power net and vehicle ground, i.e. the vehicle chassis. The impedance between the high-voltage power net and the vehicle ground may be assessed prior to activation/start-up of the high-voltage power net, i.e., prior to a high-voltage battery or other high-voltage energy source discharging. This pre-activation impedance determination may be beneficial in assessing insulation prior to operation of the high-voltage power net, however, it fails to sufficiently assess insulation concerns that may arise after activation of the high-voltage power net. Accordingly, a need exists to monitor resistance after activation of the high-voltage power net.